Recent advances in low temperature deposition techniques have created the possibility of fabricating new and/or dramatically improved devices. An impediment to the development of such devices, however, is the generally poor adhesion between low temperature films and the surface of an integrated circuit structure (e.g. a wafer or an individual IC chip) a which provides the film's substrate. In some case, alternative fabrication techniques may be used. For example, the film may be deposited on a separate substrate, which is selected on the basis of obtaining satisfactory adhesion with the film. The substrate is then trimmed and mounted close to the IC structure, so that electrical connections between the film and the IC can be made.
An example of this approach is in the fabrication of infra-red (IR) sensors and IR sensor arrays. In these devices, Lead Selenide (PbSe) films have traditionally been used as the sensor elements, which are then electrically connected to an IC chip, to form a discrete IR detector device. Ideally, it would be desirable to form Lead Selenide (PbSe) film(s) directly on the surface of the IC chip. However, because of the low adhesion between PbSe and silicon, this has not been possible. Accordingly, IR detector devices have been made by depositing the PbSe film(s) on a glass substrate. With this arrangement, the PbSe films can be supported proximal the IC chip, and electrical connections made as appropriate. While this technique enables the fabrication of IR sensors, the inability to form PbSe film(s) directly onto a silicon structure (such as an IC chip) reduces design flexibility and greatly increases costs.
Accordingly, techniques for forming low temperature films on a substrate with satisfactory adhesion remain highly desirable.